A generalized derivation of the broadening of powder pattern lines by stacking faults has been carried through allowing for fault planes of arbitrary dimensions. A minimum dimension for the fault planeTminis obtained from the measurable effective particle sizesDe(111) andDe(200). Values ofTminof the order of 200 A are obtained for samples of filings of copper, &agr; brass, and silver. The results suggest that, in the drastic cold work involved in filings, the stacking faults tend to extend over rather large distances comparable to the coherent domain dimensions.